This invention especially relates to improvements in the production of 2,3,3,3-tetrafluoro-2-propene, also known as 1234yf, and having the chemical formula:CF3—CF═CH2.This chemical compound has zero ozone depletion potential and low global-warming potential such that it may be useful and desirable as a replacement for existing materials used in refrigeration, foam blowing and other applications where fluorocarbons such as 1,1,1,2-tetrafluoroethane, also known as 134a, and known also by the chemical formula; CH2F—CF3, are currently utilized.
WO 2009/138764 discloses a process for the preparation of 1234yf comprising four steps; (1) contacting 1,1,2,3,3,3-hexafluoropropene (1216) with hydrogen in the presence of a hydrogenation catalyst to produce 1,1,2,3,3,3-hexafluoropropane (236ea); (2) dehydrofluorinating 236ea to produce 1,2,3,3,3-pentafluoropropene (1225ye); (3) contacting 1225ye with hydrogen in the presence of a hydrogenation catalyst to produce 1,2,3,3,3-pentafluoropropane (245eb); and (4) dehydrofluorinating (245eb) to produce (1234yf). Part of the process includes the use of H2SO4 in a drying tower for removal of water from the reactants.
It is known in the art to produce 1234yf from 1,1,2,3-tetrachloropropene (TCP or CCl2═CCl—CH2Cl) using a non-integrated three step route; see for example US Patent Pub. No. 2007/0197842, the disclosure of which is hereby incorporated herein by reference:TCP+3HF→1233xf+3HCl(where 1233xf is CH2═CCl—CF3)1233xf→244bb(where 244bb is CF3—CFCl—CH3)244bb→1234yf+HCl